A physician scale, often called a balance beam scale, is a mechanical instrument that determines weight by balancing an unknown mass against known counterweights. This principle makes it a common fixture in medical offices and health facilities where precise measurements are needed. The following instructions explain how to properly use and interpret the readings from this device.
Understanding the Scale Components
The scale uses three main components to achieve equilibrium. The Main Beam is the lower, longer bar, typically marked in large, 50-pound increments. This beam accounts for the bulk of the person’s weight and provides the approximate measurement.
The Minor Beam is the upper, shorter bar, marked with finer increments, often in single pounds and fractions. The precision of the final measurement is determined by the position of the sliding weight on this beam. Both beams host a Poise, which is a sliding weight that locks into calibrated notches to represent the measured mass.
Preparing the Scale for Accuracy
Before use, the scale must be zeroed to ensure accuracy. First, slide both the large poise on the main beam and the small poise on the minor beam to their far left positions, resting them against the zero mark. With the poises at zero, the horizontal balance beam should settle perfectly level, with its pointer floating freely in the center of the indicator slot, often called the trig-loop. If the pointer rests too high or too low, the scale needs adjustment. A small calibration screw or knob, usually located near the base, is turned to raise or lower the balance point until the pointer is centered.
The Step-by-Step Reading Process
Once the scale is zeroed, the subject should step onto the platform and stand still, centered on the base. The balance beam will immediately rise. To begin the measurement, engage the large poise on the main beam. Slide this large weight to the right until the balance beam drops downward, signifying the setting is more than the actual weight. Then, slide the large poise back one notch to the last mark that kept the beam resting high. This sets the main beam to the largest increment just under the true measurement.
Next, use the small poise on the minor beam for fine-tuning. Slowly slide the small poise to the right, moving it notch by notch. The correct measurement is achieved when the beam settles and the pointer floats exactly in the middle of the trig-loop, moving neither to the top nor the bottom. This centered position indicates that the sliding weights perfectly counteract the subject’s mass.
Calculating the Final Measurement
The final step is to combine the readings from both poises. The main beam provides the largest portion of the total measurement. For instance, if the large poise is locked into the notch marked 150, that represents 150 pounds. The reading from the minor beam is then added to this amount to determine the precise total. The minor beam uses smaller hash marks, often representing quarter-pound increments (0.25, 0.50, and 0.75 pounds). If the small poise rests at the mark indicating 5 and three-quarters, the total reading is 150 pounds from the main beam plus 5.75 pounds from the minor beam, totaling 155.75 pounds.